For example, a picking system, which performs a speed control on a conveying device in accordance with a supplied amount of workpieces, has been known as disclosed in, Japanese Laid-open Patent Publication No. 2000-289852.
However, there was a possibility that the picking system fails in the picking of workpieces. For example, when workpieces are conveyed in the state where they are overlapped, the conventional picking system determines that the overlapped workpieces are defectives and does not perform a holding operation to be performed by a robot. For this reason, there was a possibility that the picking system may not pick workpieces that are non-defective units.